Digital television transmitting system and receiving system and method of processing broadcast data

ABSTRACT

A digital television receiving system includes a first known data detector, a second known data detector, and a selector. The first known data detector detects a location of a first known data sequence in a broadcast signal by calculating a first correlation value between the broadcast signal and a first reference known data sequence. Similarly, the second known data detector detects a location of a second known data sequence in the broadcast signal by calculating a second correlation value between the broadcast signal and a second reference known data sequence. The selector selects the location information detected by one of the first and second known data detectors with a greater correlation value.

This application is a continuation of U.S. application Ser. No.11/760,656, filed on Jun. 8, 2007, now U.S. Pat. No. 7,839,950, whichclaims the benefit of Korean Patent Application No. 10-2006-0052095,filed on Jun. 9, 2006 and the benefit of U.S. Provisional ApplicationNo. 60/884,200, filed on Jan. 9, 2007, which are all hereby incorporatedby reference herein in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to digital television (DTV) systems andmethods of processing broadcast data.

2. Discussion of the Related Art

Presently, the technology for processing digital signals is beingdeveloped at a vast rate, and, as a larger number of the population usesthe Internet, digital electric appliances, computers, and the Internetare being integrated. Therefore, in order to meet with the variousrequirements of the users, a system that can transmit diversesupplemental information in addition to video/audio data through adigital television channel needs to be developed.

Some users may assume that supplemental data broadcasting would beapplied by using a PC card or a portable device having a simple in-doorantenna attached thereto. However, when used indoors, the intensity ofthe signals may decrease due to a blockage caused by the walls ordisturbance caused by approaching or proximate mobile objects.Accordingly, the quality of the received digital signals may bedeteriorated due to a ghost effect and noise caused by reflected waves.However, unlike the general video/audio data, when transmitting thesupplemental data, the data that is to be transmitted should have a lowerror ratio. More specifically, in case of the video/audio data, errorsthat are not perceived or acknowledged through the eyes or ears of theuser can be ignored, since they do not cause any or much trouble.Conversely, in case of the supplemental data (e.g., program executionfile, stock information, etc.), an error even in a single bit may causea serious problem. Therefore, a system highly resistant to ghost effectsand noise is required to be developed.

The supplemental data are generally transmitted by a time-divisionmethod through the same channel as the video/audio data. However, withthe advent of digital broadcasting, digital television receiving systemsthat receive only video/audio data are already supplied to the market.Therefore, the supplemental data that are transmitted through the samechannel as the video/audio data should not influence the conventionalreceiving systems that are provided in the market. In other words, thismay be defined as the compatibility of broadcast system, and thesupplemental data broadcast system should be compatible with thebroadcast system. Herein, the supplemental data may also be referred toas enhanced data. Furthermore, in a poor channel environment, thereceiving performance of the conventional receiving system may bedeteriorated. More specifically, resistance to changes in channels andnoise is more highly required when using portable and/or mobilereceiving systems.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a DTV transmittingsystem and a DTV receiving system and a method of processing broadcastdata that substantially obviate one or more problems due to limitationsand disadvantages of the related art.

An object of the present invention is to provide a DTV transmittingsystem and a DTV receiving system and a method of processing broadcastdata that are highly resistant to channel changes and noise.

Another object of the present invention is to provide a DTV transmittingsystem and a DTV receiving system and a method of processing broadcastdata that can efficiently initialize a memory of a trellis encoder inorder to enhance the receiving performance of a receiving system.

A further object of the present invention is to provide a DTVtransmitting system and a DTV receiving system and a method ofprocessing broadcast data that can detect known data beingtrellis-encoded and transmitted and that can use the detected known dataon frequency synchronization so as to enhance the receiving performance.

Additional advantages, objects, and features of the invention will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objectives and other advantages of the invention may berealized and attained by the structure particularly pointed out in thewritten description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein, adigital television (DTV) transmitting system includes a pre-processor, amultiplexer, a first Reed-Solomon (RS) encoder, a trellis encodingmodule, a second Reed-Solomon (RS) encoder, and a parity replacer. Thepre-processor pre-processes enhanced data and outputs enhanced datapackets including a known data sequence. The multiplexer multiplexes theenhanced data packets with main data packets. The first RS encoderperforms RS encoding on the multiplexed data packets by addingsystematic parity data to each main data packet and adding firstnon-systematic parity data to each enhanced data packet. The trellisencoding module performs trellis encoding on the RS-encoded datapackets. In addition, the trellis encoding module generatesinitialization data to initialize at least one of memories when theknown data sequence is inputted into the trellis encoding module fromthe first RS encoder.

The second RS encoder receives an enhanced data packet including theknown data sequence from the first RS encoder and removes the firstparity data from the received enhanced data packet. Thereafter, thesecond RS encoder replaces a portion of the known data sequence with theinitialization data and generates second non-systematic parity databased on the enhanced data packet including the replaced initializationdata. Finally, the parity replacer receives an enhanced data packetincluding the known data sequence from the first RS encoder and replacesthe first parity data in the received enhanced data packet with thesecond parity data generated by the second RS encoder.

In another aspect of the present invention, a digital television (DTV)receiving system includes a first known data detector, a second knowndata detector, and a selector. The first known data detector detects alocation of a first known data sequence in a broadcast signal bycalculating a first correlation value between the broadcast signal and afirst reference known data sequence. Similarly, the second known datadetector detects a location of a second known data sequence in thebroadcast signal by calculating a second correlation value between thebroadcast signal and second reference known data sequence. The detectorthen selects the location information detected by one of the first andsecond known data detectors with a greater correlation value. The firstreference known data sequence is a known data sequence generated basedon a assumption that an initial state of a memory included in a trellisencoder of a digital television (DTV) transmitting system for pre-codingis set to 0, and the second reference known data sequence is a knowndata sequence generated based on an assumption that the initial state ofthe memory is set to 1.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention. In the drawings:

FIG. 1 illustrates a block diagram of a digital broadcast transmittingsystem according to an embodiment of the present invention;

FIG. 2 and FIG. 3 illustrate another examples of data configuration atbefore and after ends of a data deinterleaver in a transmitting systemaccording to the present invention;

FIG. 4 illustrates a detailed block diagram of a trellis-encoding moduleshown in FIG. 1;

FIG. 5 and FIG. 6 respectively illustrate a trellis encoder and a mappershown in FIG. 4;

FIG. 7 illustrates an input symbol for initializing a memory within thetrellis encoder of FIG. 4 according to an embodiment of the presentinvention;

FIG. 8 illustrates an input symbol for initializing a memory within thetrellis encoder of FIG. 4 according to another embodiment of the presentinvention;

FIG. 9 illustrates a block diagram showing a structure of a demodulatingunit within a digital broadcast receiving system according to anembodiment of the present invention;

FIG. 10 illustrates a block diagram showing a known data estimator ofFIG. 9;

FIG. 11 illustrates a block diagram showing a known data detector ofFIG. 10;

FIG. 12 illustrates a block diagram showing a partial correlator of FIG.11;

FIG. 13 illustrates a block diagram of a digital broadcast receivingsystem according to an embodiment of the present invention; and

FIG. 14 illustrates a block diagram of a digital broadcast receivingsystem according to another embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts. In addition,although the terms used in the present invention are selected fromgenerally known and used terms, some of the terms mentioned in thedescription of the present invention have been selected by the applicantat his or her discretion, the detailed meanings of which are describedin relevant parts of the description herein. Furthermore, it is requiredthat the present invention is understood, not simply by the actual termsused but by the meaning of each term lying within.

In the present invention, the enhanced data may either consist of dataincluding information such as program execution files, stockinformation, weather forecast, and so on, or consist of video/audiodata. Additionally, the known data refer to data already known basedupon a pre-determined agreement between the transmitting system and thereceiving system. Furthermore, the main data consist of data that can bereceived from the conventional receiving system, wherein the main datainclude video/audio data. The present invention relates to a method ofinserting known data and initializing a memory of a trellis encoder in adigital broadcast receiving system, and to a method of detecting knowndata in a digital broadcast transmitting system.

FIG. 1 illustrates an example of a digital broadcast transmitting systemaccording to the present invention for inserting and transmitting knowndata. The transmitting system of FIG. 1 is merely exemplary proposed tofacilitate the understanding of the present invention. Herein, anytransmitting system that requires the transmission of transmissionparameters may be adopted in the present invention. Therefore, thepresent invention is not limited to the example proposed in thedescription set forth herein.

The digital broadcast transmitting system of FIG. 1 includes apre-processor 110, a packet multiplexer 121, a data randomizer 122, a RSencoder/non-systematic RS encoder 123, a data interleaver 124, a parityreplacer 125, a non-systematic RS encoder 126, a trellis-encoding module127, a frame multiplexer 128, and a transmitting unit 130. Thepre-processor 110 includes a randomizer 111, a RS frame encoder 112, ablock processor 113, a group formatter 114, a data deinterleaver 115,and a packet formatter 116. In the above-described structure of thepresent invention, the main data are inputted to the packet multiplexer121, and the enhanced data are inputted to the pre-processor 110, whichperforms additional encoding so that the enhanced data can respond moreeffectively to noise and channel environment that undergoes frequentchanges.

The randomizer 111 of the pre-processor 110 receives enhanced data andrandomizes the received data, thereby outputting the processed enhanceddata to the RS frame encoder 112. Then, the randomizer 111 randomizesthe received enhanced data and performs byte expansion on the randomizedenhanced data by inserting null data. At this point, by having therandomizer 111 randomize the enhanced data, a later randomizing processon the enhanced data performed by a randomizer 122, which is positionedin a later block, may be omitted. The randomizer of the conventionalATSC system may be identically used as the randomizer for randomizingthe enhanced data. Alternatively, any other type of randomizer may alsobe used for this process.

The RS frame encoder 112 receives the randomized enhanced data so as toconfigure a frame for additional encoding. Then, the RS frame encoder112 encodes the newly configured frame which is then outputted to theblock process 113. For example, the RS frame encoder 112 performs atleast one of an error correction encoding process and an error detectionencoding process on the inputted enhanced data so as to providerobustness on the corresponding data. Herein, RS encoding is applied asthe error correction encoding process, and cyclic redundancy check (CRC)encoding is applied as the error detection encoding process. Whenperforming RS encoding, parity data that are to be used for errorcorrection are generated. And, when performing CRC encoding, CRC datathat are to be used for error detection are generated. Furthermore, byscattering a group error that may occur due to a change in the frequencyenvironment, the RS frame encoder 112 may also perform a row permutationprocess, which permutes enhanced data having a predetermined size in rowunits, so that the corresponding data can respond to the severelyvulnerable and frequently changing frequency environment.

The block processor 113 encodes the enhanced data outputted from the RSframe encoder 112 at a coding rate of M/N and transmits the encoded datato the group formatter 114. For example, if 1 bit of the enhanced datais encoded to 2 bits and outputted, then M is equal to 1 and N is equalto 2 (i.e., M=1 and N=2). Alternatively, if 1 bit of the enhanced datais encoded to 4 bits and outputted, then M is equal to 1 and N is equalto 4 (i.e., M=1 and N=4).

The group formatter 114 inserts the enhanced data outputted from theblock processor 113 (herein, the enhanced data may include supplementalinformation data such as signaling information including transmissioninformation) in a corresponding area within the data group, which isconfigured according to a pre-defined rule. Furthermore, in relationwith the data deinterleaving process, various types of places holders orknown data are also inserted in corresponding areas within the datagroup.

At this point, the data group may be described by at least onehierarchical area. Herein, the data allocated to the each area may varydepending upon the characteristic of each hierarchical area.Additionally, each data group may be configured to include a fieldsynchronization signal.

In an example given in the present invention, a data group is dividedinto A, B, and C regions in a data configuration prior to datadeinterleaving.

FIG. 2 illustrates an alignment of data after being data interleaved andidentified, and FIG. 3 illustrates an alignment of data before beingdata interleaved and identified. More specifically, a data structureidentical to that shown in FIG. 2 is transmitted to a receiving system.Also, the data group configured to have the same structure as the datastructure shown in FIG. 2 is inputted to the data deinterleaver 115.

As described above, FIG. 2 illustrates a data structure prior to datadeinterleaving that is divided into 3 regions, such as region A, regionB, and region C. Also, in the present invention, each of the regions Ato C is further divided into a plurality of regions. Referring to FIG.2, region A is divided into 5 regions (A1 to A5), region B is dividedinto 2 regions (B1 and B2), and region C is divided into 3 regions (C1to C3). Herein, regions A to C are identified as regions having similarreceiving performances within the data group. Herein, the type ofenhanced data, which are inputted, may also vary depending upon thecharacteristic of each region.

In the example of the present invention, the data structure is dividedinto regions A to C based upon the level of interference of the maindata. Herein, the data group is divided into a plurality of regions tobe used for different purposes. More specifically, a region of the maindata having no interference or a very low interference level may beconsidered to have a more resistant (or stronger) receiving performanceas compared to regions having higher interference levels. Additionally,when using a system inserting and transmitting known data in the datagroup, and when consecutively long known data are to be periodicallyinserted in the enhanced data, the known data having a predeterminedlength may be periodically inserted in the region having no interferencefrom the main data (e.g., region A). However, due to interference fromthe main data, it is difficult to periodically insert known data andalso to insert consecutively long known data to a region havinginterference from the main data (e.g., region B and region C).

Hereinafter, examples of allocating data to region A (A1 to A5), regionB (B1 and B2), and region C (C1 to C3) will now be described in detailwith reference to FIG. 2. The data group size, the number ofhierarchically divided regions within the data group and the size ofeach region, and the number of enhanced data bytes that can be insertedin each hierarchically divided region of FIG. 2 are merely examplesgiven to facilitate the understanding of the present invention. Herein,the group formatter 114 creates a data group including places in whichfield synchronization bytes are to be inserted, so as to create the datagroup that will hereinafter be described in detail.

More specifically, region A is a region within the data group in which along known data sequence may be periodically inserted, and in whichincludes regions wherein the main data are not mixed (e.g., A1 to A5).Also, region A includes a region (e.g., A1) located between a fieldsynchronization region and the region in which the first known datasequence is to be inserted. The field synchronization region has thelength of one segment (i.e., 832 symbols) existing in an ATSC system.

For example, referring to FIG. 2, 2428 bytes of the enhanced data may beinserted in region A1, 2580 bytes may be inserted in region A2, 2772bytes may be inserted in region A3, 2472 bytes may be inserted in regionA4, and 2772 bytes may be inserted in region A5. Herein, trellisinitialization data or known data, MPEG header, and RS parity are notincluded in the enhanced data. As described above, when region Aincludes a known data sequence at both ends, the receiving system useschannel information that can obtain known data or field synchronizationdata, so as to perform equalization, thereby providing enforcedequalization performance.

Also, region B includes a region located within 8 segments at thebeginning of a field synchronization region within the data group(chronologically placed before region A1) (e.g., region B1), and aregion located within 8 segments behind the very last known datasequence which is inserted in the data group (e.g., region B2). Forexample, 930 bytes of the enhanced data may be inserted in the regionB1, and 1350 bytes may be inserted in region B2. Similarly, trellisinitialization data or known data, MPEG header, and RS parity are notincluded in the enhanced data. In case of region B, the receiving systemmay perform equalization by using channel information obtained from thefield synchronization section. Alternatively, the receiving system mayalso perform equalization by using channel information that may beobtained from the last known data sequence, thereby enabling the systemto respond to the channel changes.

Region C includes a region located within 30 segments including andpreceding the 9^(th) segment of the field synchronization region(chronologically located before region A) (e.g., region C1), a regionlocated within 12 segments including and following the 9^(th) segment ofthe very last known data sequence within the data group (chronologicallylocated after region A) (e.g., region C2), and a region located in 32segments after the region C2 (e.g., region C3). For example, 1272 bytesof the enhanced data may be inserted in the region C1, 1560 bytes may beinserted in region C2, and 1312 bytes may be inserted in region C3.Similarly, trellis initialization data or known data, MPEG header, andRS parity are not included in the enhanced data. Herein, region C (e.g.,region C1) is located chronologically earlier than (or before) region A.

Since region C (e.g., region C1) is located further apart from the fieldsynchronization region which corresponds to the closest known dataregion, the receiving system may use the channel information obtainedfrom the field synchronization data when performing channelequalization. Alternatively, the receiving system may also use the mostrecent channel information of a previous data group. Furthermore, inregion C (e.g., region C2 and region C3) located before region A, thereceiving system may use the channel information obtained from the lastknown data sequence to perform equalization. However, when the channelsare subject to fast and frequent changes, the equalization may not beperformed perfectly. Therefore, the equalization performance of region Cmay be deteriorated as compared to that of region B.

When it is assumed that the data group is allocated with a plurality ofhierarchically divided regions, as described above, the block processor113 may encode the enhanced data, which are to be inserted to eachregion based upon the characteristic of each hierarchical region, at adifferent coding rate. For example, the block processor 113 may encodethe enhanced data, which are to be inserted regions A1 to A5 of regionA, at a coding rate of 1/2. Then, the group formatter 114 may insert the1/2-rate encoded enhanced data to regions A1 to A5.

The block processor 113 may encode the enhanced data, which are to beinserted in regions B1 and B2 of region B, at a coding rate of 1/4having higher error correction ability as compared to the 1/2-codingrate. Then, the group formatter 114 inserts the 1/4-rate coded enhanceddata in region B1 and region B2. Furthermore, the block processor 113may encode the enhanced data, which are to be inserted in regions C1 toC3 of region C, at a coding rate of 1/4 or a coding rate having highererror correction ability than the 1/4-coding rate. Then, the groupformatter 114 may either insert the encoded enhanced data to regions C1to C3, as described above, or leave the data in a reserved region forfuture usage.

In addition, the group formatter 114 also inserts supplemental data,such as signaling information that notifies the overall transmissioninformation, other than the enhanced data in the data group. Also, apartfrom the encoded enhanced data outputted from the block processor 113,the group formatter 114 also inserts MPEG header place holders,non-systematic RS parity place holders, main data place holders, whichare related to data deinterleaving in a later process, as shown in FIG.2. Herein, the main data place holders are inserted because the enhanceddata bytes and the main data bytes are alternately mixed with oneanother in regions B and C based upon the input of the datadeinterleaver, as shown in FIG. 2. For example, based upon the dataoutputted after data deinterleaving, the place holder for the MPEGheader may be allocated at the very beginning of each packet.

Furthermore, the group formatter 114 either inserts known data generatedin accordance with a pre-determined method or inserts known data placeholders for inserting the known data in a later process. Additionally,place holders for initializing the trellis encoder 127 are also insertedin the corresponding regions. For example, the initialization data placeholders may be inserted in the beginning of the known data sequence.Herein, the size of the enhanced data that can be inserted in a datagroup may vary in accordance with the sizes of the trellisinitialization place holders or known data (or known data placeholders), MPEG header place holders, and RS parity place holders.

The output of the group formatter 114 is inputted to the datadeinterleaver 115. And, the data deinterleaver 115 deinterleaves data byperforming an inverse process of the data interleaver on the data andplace holders within the data group, which are then outputted to thepacket formatter 116. More specifically, when the data and place holderswithin the data group configured, as shown in FIG. 2, are deinterleavedby the data deinterleaver 115, the data group being outputted to thepacket formatter 116 is configured to have the structure shown in FIG.3.

Among the data deinterleaved and inputted, the packet formatter 116removes the main data place holder and RS parity place holder that wereallocated for the deinterleaving process from the inputted deinterleaveddata. Thereafter, the remaining portion of the corresponding data isgrouped, and 4 bytes of MPEG header are inserted therein. The 4-byteMPEG header is configured of a 1-byte MPEG synchronization byte added tothe 3-byte MPEG header place holder.

When the group formatter 114 inserts the known data place holder, thepacket formatter 116 may either insert actual known data in the knowndata place holder or output the known data place holder without anychange or modification for a replacement insertion in a later process.Afterwards, the packet formatter 116 divides the data within theabove-described packet-formatted data group into 188-byte unit enhanceddata packets (i.e., MPEG TS packets), which are then provided to thepacket multiplexer 121.

The packet multiplexer 121 multiplexes the 188-byte unit enhanced datapacket and main data packet outputted from the packet formatter 116according to a pre-defined multiplexing method. Subsequently, themultiplexed data packets are outputted to the data randomizer 122. Themultiplexing method may be modified or altered in accordance withdiverse variables of the system design. One of the multiplexing methodsof the packet multiplexer 121 is to identify an enhanced data burstsection and a main data section along a time axis and alternatelyrepeating the two sections. At this point, at least one data group maybe transmitted from the enhanced data burst section, and only the maindata may be transmitted from the main data section. Herein, the enhanceddata burst section may also transmit main data.

As described above, if the enhanced data are transmitted in the burststructure, the receiving system receiving only the enhanced data turnsthe power on only during the burst section in order to receive theenhanced data. Alternatively, the receiving system turns the power offduring the remaining section, which corresponds to the main data sectiontransmitting only the main data, so that the receiving system does notreceive any portion of the main data. Thus, power consumption of thereceiving system may be reduced.

If the inputted data correspond to the main data packet, the datarandomizer 122 performs the same randomizing process as the conventionalrandomizer. More specifically, the data randomizer 122 discards (orremoves) the MPEG synchronization byte included in the main data packetand randomizes the remaining 187 byte by using a pseudo random byte thatis generated by the data randomizer 122. Then, the randomized data bytesare outputted to the RS encoder/non-systematic RS encoder 123. However,if the inputted data correspond to the enhanced data packet, the datarandomizer 522 discards (or removes) the MPEG synchronization byte fromthe 4-byte MPEG header included in the enhanced data packet andrandomizes only the remaining 3 bytes. Also, the data randomizer 122outputs the remaining portion of enhanced data excluding the MPEG headerto the RS encoder/non-systematic RS encoder 123 without performing therandomizing process. This is because the randomizer 111 has alreadyperformed a randomizing process on the enhanced data in an earlierprocess. The known data and the initialization data place holdersincluded in the enhanced data packet may either be randomized or not berandomized.

The RS encoder/non-systematic RS encoder 123 RS-encodes the datarandomized by the data randomizer 122 or the data bypassing the datarandomizer 122 so as to add 20 bytes of RS parity to the correspondingdata. Then, the RS encoder/non-systematic RS encoder 123 outputs theprocessed data to the data interleaver 124. At this point, if theinputted data correspond to the main data packet, the RSencoder/non-systematic RS encoder 123 performs a systematic RS-encodingprocess identical to that of the conventional broadcasting system,thereby adding 20 bytes of RS parity at the end of the 187-byte unitdata. Alternatively, if the inputted data correspond to the enhanceddata packet, the RS encoder/non-systematic RS encoder 123 performs anon-systematic RS-encoding process at a specific parity byte placewithin the enhanced data packet, thereby inserting the 20-byte RSparity. Herein, the data interleaver 124 corresponds to a byte unitconvolutional interleaver. The output of the data interleaver 124 isinputted to the parity replacer 125 and the non-systematic RS encoder126.

Meanwhile, a process of initializing a memory within thetrellis-encoding module 127 is primarily required in order to decide theoutput data of the trellis-encoding module 127, which is located afterthe parity replacer 125, as the known data pre-defined according to anagreement between the receiving system and the transmitting system. Morespecifically, the memory of the trellis-encoding module 127 should firstbe initialized before the received known data sequence istrellis-encoded. The memory of the trellis-encoding module 127 isinitialized because various types of sequences may be outputteddepending upon the memory status of the trellis-encoding module 127,even though the known data sequence is inputted to the trellis-encodingmodule 127.

At this point, the beginning portion of the known data sequence that isbeing received corresponds to the initialization data place holder andnot the actual known data. Herein, the initialization data place holderhas been included in the data by the group formatter 114 in an earlierprocess. Therefore, the process of generating initialization data andreplacing the initialization data place holder of the correspondingmemory with the generated initialization data are required to beperformed immediately before the known data sequence being inputted istrellis-encoded.

Additionally, a value of the initialization data is decided andgenerated based upon a memory status of the trellis-encoding module 127.Further, due to the newly replaced initialization data, a process ofnewly calculating the RS parity and replacing the RS parity, which isoutputted from the data interleaver 124, with the newly calculated RSparity is required. Therefore, the non-systematic RS encoder 126receives the enhanced data packet including the initialization dataplace holder, which is to be replaced with the actual initializationdata, from the data interleaver 124 and also receives the initializationdata from the trellis-encoding module 127. Among the inputted enhanceddata packet, the initialization data place holder is replaced with theinitialization data, and the RS parity data that are added to theenhanced data packet are removed. Thereafter, a new non-systematic RSparity is calculated and outputted to the parity replacer 125.Accordingly, the parity replacer 125 selects the output of the datainterleaver 124 as the data within the enhanced data packet, and theparity replacer 125 selects the output of the non-systematic RS encoder126 as the RS parity. The selected data are then outputted to thetrellis-encoding module 127.

Meanwhile, if the main data packet is inputted or if the enhanced datapacket, which does not include any initialization data place holder thatis to be replaced, is inputted, the parity replacer 125 selects the dataand RS parity that are outputted from the data interleaver 124. Then,the parity replacer 125 directly outputs the selected data to thetrellis-encoding module 127 without any modification. Thetrellis-encoding module 127 receives the output data of the parityreplacer 125 or the initialization data and converts the received datato symbol units. Then, the trellis-encoding module 127 pre-codes theupper bit of the converted symbol and trellis-encodes the lower bit ofthe converted symbol. Thereafter, trellis-encoding module 127 outputsthe processed data to the frame multiplexer 128. The operation of thetrellis-encoding module 127 will be described in more detail in a laterprocess.

The frame multiplexer 128 inserts a field synchronization signal and asegment synchronization signal to the data outputted from thetrellis-encoding module 127 and, then, outputs the processed data to thetransmitting unit 130. Herein, the transmitting unit 130 includes apilot inserter 131, a modulator 132, and a radio frequency (RF)up-converter 133. The operations and roles of the transmitting unit 130and its components are identical to those of the conventionaltransmitter. Therefore, detailed description of the same will be omittedfor simplicity.

Trellis-Encoding

FIG. 4 illustrates a detailed block diagram of a trellis-encoding module127, which can be initialized. Herein, when a known data symbol sequencein inputted, the memory within the trellis-encoding module 127 isinitialized so that the trellis-encoded known data symbol sequencebecomes the desired known data symbol sequence. In order to do so, thetrellis-encoding module 127 includes a multiplexer 201, aninitialization data generator 202, and a trellis encoder 203.

Referring to FIG. 4, in the trellis-encoding module 127 having theabove-described structure, when initialization of the memory within thetrellis-encoding module 127 is required, the initialization datagenerator 202 generates data required for the initialization processbased upon a value of the memory within the trellis encoder 203.Thereafter, the initialization data generator 202 outputs the generatedinitialization data to the multiplexer 201 and a non-systematic RSencoder 126. More specifically, of the data being inputted for thetrellis-encoding process correspond to initialization data place holders(or the beginning of the known data sequence), the initialization datagenerator 202 generates the initialization data.

The multiplexer 201 selects one of the output data of the parityreplacer 125 and the initialization data of the initialization datagenerator 202. Then, the multiplexer 201 outputs the selected data tothe trellis encoder 203. More specifically, when the memory of thetrellis encoder 203 is required to be initialized, the initializationdata are outputted to the trellis encoder 203 instead of theinitialization data place holders (or the beginning of the known datasequence) outputted from the parity replacer 125. Accordingly, thememory within the trellis encoder 203 is initialized to the valuedecided by the initialization data. Then, from the point (or moment) thememory of the trellis encoder 203 is initialized, the data outputtedfrom the trellis encoder 203 may become a known data sequence encoded tohave a data format (or configuration) desired by the transmitting systemand the receiving system.

FIG. 5 and FIG. 6 respectively illustrate the trellis encoder 203according to an embodiment of the present invention. Herein, the outputdata of the parity replacer 125 or the initialization data aretrellis-encoded in symbol units. Each symbol is configured of 2 bits.More specifically, an upper bit d1 of the input symbol is pre-coded byusing a memory m2 and an adder of a pre-coder, as shown in FIG. 5 andFIG. 6, so as to be outputted as c2. A lower bit d0 of the input symbolis trellis-encoded by using memories m1 and m0 and an adder, so as to beoutputted as c1 and c0. The output c2c1c0 of the trellis encoder 203corresponds to an 8-level signal, as shown in FIG. 6, which is mapped toa VSE signal and outputted to a frame multiplexer 128.

Therefore, the memory m2 of the trellis encoder 203 is decided onlybased upon d1, and the memories m1 and m0 are decided only based upondo. In other words, the upper bit c2 of the output data of the trellisencoder 203 is decided based upon the memory m2 within the pre-coder andthe upper input bit d1, and the two lower bits c1 and c0 are decidedbased upon the memories m1 and m0 and the lower input bit d0. Thepresent invention will now be described in detail in accordance withfirst and second embodiments of the present invention. The first andsecond embodiments respectively describe an example of initializing onlymemories m1m0 and an example of initializing all memories m2m1m0.

First Embodiment

When the memory m2 of the pre-coder within the trellis encoder 203 isnot initialized, and when only the remaining two memories m1 and m0 areinitialized, regardless of whether known data are inputted after theinitialization process, only the two lower bits c1 and c0 among the 3bits outputted from the trellis encoder 203 correspond to the knowndata. And, the one upper bit c2 may have two different values dependingupon the status of the memory m2 within the pre-coder. FIG. 7illustrates the output data of the initialization data generator 202,when initializing the memories m1 and m0 of the trellis encoder 203.More specifically, FIG. 7 illustrates the input data of two symbolsections that are to be initialized to ‘00’, when each of the memoriesm1 and m0 of the trellis encoder 203 is in an arbitrary status. Forexample, when the memory status corresponds to m1m0=11, the input bit d0should be consecutively inputted as ‘1’ and ‘1’ in order to initializethe memory to ‘00’. In this case, the initialization data generator 202generates data required for the initialization process based upon thevalue of the memory m1m0 of the trellis encoder 203. At this point, ifthe memory m1m0 of the trellis encoder 203 is to be initialized to astatus other than ‘00’, two symbol sequences that are different fromthose shown in FIG. 7 are required. Since these two different symbolsequences may be easily deduced, a detailed description of the same willbe omitted for simplicity.

As described above, when only the memories m1 and m0 of the trellisencoder 203 are initialized to a decided value, if a known data symbolsequence is inputted to the trellis encoder 203, c1 and c0 still remainas known data. However, c2 may be modified (or changed) in accordancewith the value of the memory m2 within the pre-coder. Since thepre-coder is configured to have a feed-back structure, even though anidentical d1 of the data sequence is inputted, the data sequence of theoutputted data may become opposite to one another if the starting pointis not the same.

The operation of the pre-coder will now be described in detail. When aninitial state of the memory m2 within the pre-coder corresponds to ‘0’,and when 100111 is inputted as the data sequence of input bit d1, thedata sequence of the output c2 of the pre-coder becomes 111010. However,when the initial state of the memory m2 within the pre-coder correspondsto ‘1’, and when 100111 is inputted as the data sequence of input bitd1, the data sequence of the output c2 of the pre-coder becomes 000101.More specifically, when the same data sequence is inputted to thepre-coder, and when the initial state of the memory m2 within thepre-coder is opposite to one another, the output c2 also becomes theopposite of one another. As a result, when the known data sequence isinputted, and when only the memories m1 and m0 of the trellis encoder203 are initialized, two different symbol sequences may be outputtedfrom the output data of the trellis encoder 203. And, at this point,only c2 of the two output symbol sequences is the opposite of oneanother, and c1 and c0 are identical to one another, respectively.

Therefore, the known data symbol being trellis-encoded and mapped to 8levels may correspond to level +7 (c2c1c0=111) or level −1 (c2c1c0=011),or correspond to level +5 (c2c1c0=110) or level −3 (c2c1c0=010) orcorrespond to level +3 (c2c1c0=101) or level −5 (c2c1c0=001), orcorrespond to level +1 (c2c1c0=100) or level −7 (c2c1c0=000). Morespecifically, when c1c0 is equal to 00, the signal level being mapped to8 different levels may only correspond to −7 and +1. As described above,depending upon the status of the memory m2 within the pre-coder, twodifferent known data symbol sequences may be outputted from the trellisencoder 203. If one of the two known data symbol sequence corresponds to−7,+5,−5,+1,+7,+3,−1,−3, the other known data symbol sequencecorresponds to +1,−3,+3,−7,−1,−5,+7,+5.

Second Embodiment

As shown in FIG. 5 and FIG. 6, in order to initialize the memory m2 ofthe trellis encoder 203 to a decided value, one d1 may be used.Alternatively, in order to initialize each of the memories m1 and m0 toa decided value, two d0s are required. Therefore, it is apparent that inorder to initialize memories m2, m1, and m0 of the trellis encoder 203,at least two input symbols are required. FIG. 8 illustrates the outputof the initialization data generator 202 when initializing the memoriesm2, m1, and m0 of the trellis encoder 203. More specifically, FIG. 8illustrates the input data of two symbol sections that are to beinitialized to ‘000’, when each of the memories m2, m1, and m0 of thetrellis encoder 203 is in an arbitrary status.

For example, when the memory status corresponds to m2m1m0=111, the inputsymbol d1d0 should be consecutively inputted either as ‘01’ and ‘11’ oras ‘11’ and ‘01’ in order to initialize the memory to ‘000’. In thiscase, the initialization data generator 202 generates data required forthe initialization process based upon the value of the memory m2m1m0 ofthe trellis encoder 203. At this point, if the memory m2m1m0 of thetrellis encoder 203 is to be initialized to a status other than ‘000’,two symbol sequences that are different from those shown in FIG. B arerequired. Since these two different symbol sequences may be easilydeduced, a detailed description of the same will be omitted forsimplicity.

Receiving System

FIG. 9 illustrates a block diagram showing a demodulating unit of adigital broadcast receiving system according to an embodiment of thepresent invention, wherein the demodulating unit is used for receivingdata transmitted from the transmitting system, demodulating andequalizing the received data, so as to recover the processed data backto the initial (or original) data. Referring to FIG. 9, the demodulatingunit of the digital broadcast receiving system includes a demodulator601, an equalizer 602, a known data estimator 603, a block decoder 604,a data deformatter 605, a RS frame decoder 606, a derandomizer 607, adata deinterleaver 608, a RS decoder 609, and a data derandomizer 610.

More specifically, an intermediate frequency (IF) signal of a particularchannel that is tuned by a tuner is inputted to the demodulator 601 andthe known data detector 603. The demodulator 601 performs self gaincontrol, carrier recovery, and timing recovery processes on the inputtedIF signal, thereby modifying the IF signal to a baseband signal. Then,the demodulator 601 outputs the newly created baseband signal to theequalizer 602 and the known data estimator 603. The equalizer 602compensates the distortion of the channel included in the demodulatedsignal and then outputs the error-compensated signal to the blockdecoder 604.

At this point, the known data estimator 603 detects the known sequenceplace inserted by the transmitting end from the input/output data of thedemodulator 601 (i.e., the data prior to the demodulation or the dataafter the modulation). Thereafter, the known data place information isoutputted to the demodulator 601 and the equalizer 602. Simultaneously,a coarse frequency offset is estimated and outputted to the demodulator601. The processes of detecting the known data place and detecting thecoarse frequency offset will be described in more detail in a laterprocess.

Also, the known data estimator 603 outputs a set of information to theblock decoder 604. This set of information is used to allow the blockdecoder 604 of the receiving system to identify the enhanced data thatare processed with additional encoding from the transmitting system andthe main data that are not processed with additional encoding. This setof information is also used to indicate a stating point of a block inthe enhanced encoder. Also, the information detected from the known dataestimator 603 may be used throughout the entire receiving system and mayalso be used by the data deformatter 605 and the RS frame decoder 606.

The demodulator 601 uses the known data during the timing and/or carrierrecovery, thereby enhancing the demodulating performance. Similarly, theequalizer 602 uses the known data sequence, thereby enhancing theequalizing quality. Particularly, the demodulator 601 may use the knowndata place information and the estimated value of the coarse frequencyoffset both outputted from the known data estimator 603, therebyestimating and compensating the frequency offset with more accuracy.Moreover, the decoding result of the block decoder 604 may be fed-backto the equalizer 602, thereby enhancing the equalizing performance.

The equalizer 602 may perform channel equalization by using a pluralityof methods. An example of estimating a channel impulse response (CIR) soas to perform channel equalization will be given in the description ofthe present invention. Most particularly, an example of estimating theCIR in accordance with each region within the data group, which ishierarchically divided and transmitted from the transmitting system, andapplying each CIR differently will also be described herein.Furthermore, by using the known data, the place and contents of which isknown in accordance with an agreement between the transmitting systemand the receiving system, and the field synchronization data, so as toestimate the CIR, the present invention may be able to perform channelequalization with more stability.

Herein, the data group that is inputted for the equalization process isdivided into regions A to C, as shown in FIG. 2. More specifically, inthe example of the present invention, each region A, B, and C arefurther divided into regions A1 to A5, regions B1 and B2, and regions C1to C3, respectively. Referring to FIG. 2, the CIR that is estimated fromthe field synchronization data in the data structure is referred to asCIR_FS. Alternatively, the CIRs that are estimated from each of the 5known data sequences existing in region A are sequentially referred toas CIR_NO, CIR_N1, CIR_N2, CIR_N3, and CIR_N4.

As described above, the present invention uses the CIR estimated fromthe field synchronization data and the known data sequences in order toperform channel equalization on data within the data group. At thispoint, each of the estimated CIRs may be directly used in accordancewith the characteristics of each region within the data group.Alternatively, a plurality of the estimated CIRs may also be eitherinterpolated or extrapolated so as to create a new CIR, which is thenused for the channel equalization process.

Herein, when a value F(Q) of a function F(x) at a particular point Q anda value F(S) of the function F(x) at another particular point S areknown, interpolation refers to estimating a function value of a pointwithin the section between points Q and S. Linear interpolationcorresponds to the simplest form among a wide range of interpolationoperations. The linear interpolation described herein is merelyexemplary among a wide range of possible interpolation methods. And,therefore, the present invention is not limited only to the examples setforth herein.

Alternatively, when a value F(Q) of a function F(x) at a particularpoint Q and a value F(S) of the function F(x) at another particularpoint S are known, extrapolation refers to estimating a function valueof a point outside of the section between points Q and S. Linearextrapolation is the simplest form among a wide range of extrapolationoperations. Similarly, the linear extrapolation described herein ismerely exemplary among a wide range of possible extrapolation methods.And, therefore, the present invention is not limited only to theexamples set forth herein.

More specifically, in case of region C1, any one of the CIR_N4 estimatedfrom a previous data group, the CIR_FS estimated from the current datagroup that is to be processed with channel equalization, and a new CIRgenerated by extrapolating the CIR_FS of the current data group and theCIR_N0 may be used to perform channel equalization. Alternatively, incase of region B1, a variety of methods may be applied as described inthe case for region C1. For example, a new CIR created by linearlyextrapolating the CIR_FS estimated from the current data group and theCIR_N0 may be used to perform channel equalization. Also, the CIR_FSestimated from the current data group may also be used to performchannel equalization. Finally, in case of region A1, a new CIR may becreated by interpolating the CIR_FS estimated from the current datagroup and CIR_N0, which is then used to perform channel equalization.Furthermore, any one of the CIR_FS estimated from the current data groupand CIR_N0 may be used to perform channel equalization.

In case of regions A2 to A5, CIR_N(i−11) estimated from the current datagroup and CIR_N(i) may be interpolated to create a new CIR and use thenewly created CIR to perform channel equalization. Also, any one of theCIR_N(i−11) estimated from the current data group and the CIR_N(i) maybe used to perform channel equalization. Alternatively, in case ofregions B2, C2, and C3, CIR_N3 and CIR_N4 both estimated from thecurrent data group may be extrapolated to create a new CIR, which isthen used to perform the channel equalization process. Furthermore, theCIR_N4 estimated from the current data group may be used to perform thechannel equalization process. Accordingly, an optimum performance may beobtained when performing channel equalization on the data inserted inthe data group. The methods of obtaining the CIRs required forperforming the channel equalization process in each region within thedata group, as described above, are merely examples given to facilitatethe understanding of the present invention. A wider range of methods mayalso be used herein. And, therefore, the present invention will not onlybe limited to the examples given in the description set forth herein.

Meanwhile, if the data being channel equalized and then inputted to theblock decoder 604 correspond to the enhanced data on which additionalencoding and trellis encoding are both performed by the transmittingsystem, trellis-decoding and additional decoding processes are performedas inverse processes of the transmitting system. Alternatively, if thedata being channel equalized and then inputted to the block decoder 604correspond to the main data on which additional encoding is notperformed and only trellis-encoding is performed by the transmittingsystem, only the trellis-decoding process is performed.

The data group decoded by the block decoder 604 is inputted to theenhanced data deformatter 605, and the main data packet is inputted tothe data deinterleaver 608.

More specifically, if the inputted data correspond to the main data, theblock decoder 604 performs Viterbi decoding on the inputted data, so asto either output a hard decision value or hard-decide a soft decisionvalue and output the hard-decided result. On the other hand, if theinputted correspond to the enhanced data, the block decoder 604 outputseither a hard decision value or a soft decision value on the inputtedenhanced data. In other words, if the data inputted to the block decoder604 correspond to the enhanced data, the block decoder 604 performs adecoding process on the data encoded by the block processor and thetrellis encoder of the transmitting system. At this point, the output ofthe RS frame encoder included in the pre-processor of the transmittingsystem becomes an external code, and the output of the block processorand the trellis encoder becomes an internal code. In order to showmaximum performance of the external code when decoding such connectioncodes, the decoder of the internal code should output a soft decisionvalue. Therefore, the block decoder 604 may output a hard decision valueon the enhanced data. However, when required, it is more preferable thatthe block decoder 604 outputs a soft decision value.

More specifically, depending upon the system design or conditions, theblock decoder 604 outputs any one of the soft decision value and thehard decision value with respect to the enhanced data, and the blockdecoder 604 outputs the hard decision value with respect to the maindata.

Meanwhile, the data deinterleaver 608, the RS decoder 609, and the dataderandomizer 610 are blocks required for receiving the main data.Therefore, the above-mentioned blocks may not be required in thestructure of a receiving system that is designed to receive only theenhanced data. The data deinterleaver 608 performs an inverse process ofthe data interleaver included in the transmitting system bydeinterleaving the main data. Then, the data deinterleaver 608 outputsthe deinterleaved data to the RS decoder 609. The RS decoder 609performs a systematic RS decoding process on the deinterleaved data andoutputs the processed data to the data derandomizer 610.

The data derandomizer 610 received the data outputted from the RSdecoder 609 and generates a pseudo random data byte identical to that ofthe randomizer included in the digital broadcast transmitting system (orDTV transmitter). Thereafter, the data derandomizer 610 performs abitwise exclusive OR (XOR) operation between the generated pseudo randomdata byte and the data packet outputted from the RS decoder 609, therebyinserting the MPEG synchronization bytes to the beginning of each packetso as to output the data in 188-byte main data packet units.

Meanwhile, the data being outputted from the block decoder 604 areinputted to the data deformatter 605 in an data group format. At thispoint, the data deformatter 605 already knows the configuration of theinputted data. Therefore, the data deformatter 605 is capable ofidentifying the signaling information, which includes systeminformation, and the enhanced data within the A area. Herein, the datadeformatter 605 removes the known data, trellis initialization data, andMPEG header that have been inserted in the main data and data group, andalso removes the RS parity data that have been inserted by the RSencoder/non-systematic RS encoder or the non-systematic RS encoder ofthe transmitting system. Thereafter, the data deformatter 605 outputsthe processed data to the RS frame decoder 606.

The RS frame decoder 606 performs an inverse process of the RS frameencoder included in the transmitting system on the output data of thedata deformatter 605. Then, the RS frame decoder 606 outputs theprocessed data to the derandomizer 607. More specifically, the RS framedecoder 606 performs at least one of error detection decoding, inversedrow permutation, and error correction decoding on the input data so asto recover the enhanced data to the initial (or original) enhanced data.The derandomizer 607 derandomizes the inputted enhanced data byperforming an inverse process of the randomizer 111 included in thetransmitting system. Meanwhile, the known data estimator 603 estimatesthe known data place inserted by the transmitting system and, at thesame time, estimates the coarse frequency offset while estimating theknown data. At this point, as shown in the first embodiment, thetransmitting system may only initialize the memories m1 and m0 of thetrellis encoder at the initialization data place holder (or the startingpoint of the known data sequence). Alternatively, as shown in the secondembodiment, the transmitting system may initialize all three memoriesm2, m1, and m0 of the trellis encoder.

Particularly, as shown in the first embodiment, when initializing onlythe memories m1 and m0 of the trellis encoder (i.e., when the memory m2within the pre-coder is not initialized), and when the known data aretrellis-encoded and outputted, two different known data sequences may beoutputted based upon the initial state of the memory m2 within thepre-coder. Therefore, the known data estimator 603 of the digitalbroadcast receiving system (or digital television receiver) may estimatethe status (or state) of the pre-coder so as to detect the known data.

In order to do so, the known data estimator 603 as shown in FIG. 10includes a first known data detector 701, a second known data detector702, and a selector 703.

The first known data detector 701 detects a known data symbol sequencethat is generated when the initial state of the memory m2 within thepre-coder of the trellis encoder included in the transmitting system is‘0’. The second known data detector 702 detects a known data symbolsequence that is generated when the initial state of the memory m2 is‘1’. For this, the first known data detector 701 calculates a partialcorrelation between the received signal and a first reference known datasequence, thereby detecting the place of the corresponding known dataand estimating the coarse frequency offset, which are then outputted.Additionally, the second known data detector 702 calculates a partialcorrelation between the received signal and a second reference knowndata sequence, thereby detecting the place of the corresponding knowndata and estimating the coarse frequency offset, which are thenoutputted. Herein, the first reference known data sequence correspondsto a reference data sequence that is generated from or stored in thereceiving system, when it is assumed that the initial state of thepre-coder memory m2 within the trellis encoder included in thetransmitting system is ‘0’. The second reference known data sequencecorresponds to a reference data sequence that is generated from orstored in the receiving system, when it is assumed that the initialstate of the pre-coder memory m2 within the trellis encoder included inthe transmitting system is ‘1’.

The selector 703 compares each peak value of the partial correlationvalues respectively outputted from the first known data detector 701 andthe second known data detector 702. Thereafter, the selector 703 selectsthe known data detector having the higher (or greater) peak value. The,the selector 703 outputs the known data place information, frequencyoffset, and selected information (e.g., estimated initial state value ofthe pre-coder memory), which are outputted from the selected known datadetector. Since the components and operation of the first known datadetector 701 and the second known data detector 702 are identical to oneanother, the description of only one known data detector according tothe present invention will be provided herein.

FIG. 11 illustrates a block diagram shown the structure of a known datadetector. More specifically, FIG. 11 illustrates an example an inputtedsignal being oversampled to N times its initial state. Herein, Nrepresents a sampling rate of the received signal. Referring to FIG. 11,the known sequence detector includes N number of partial correlators 811to 81N configured in parallel, and a known data place detector andfrequency offset decider 820. Herein, the first partial correlator 811consists of a 1/N decimator, and a partial correlator. The secondpartial correlator 812 consists of a 1 sample delay, a 1/N decimator,and a partial correlator. And, the N^(th) partial correlator 81Nconsists of a N−1 sample delay, a 1/N decimator, and a partialcorrelator. These are used to match (or identify) the phase of each ofthe samples within the oversampled symbol with the phase of the originalsymbol, and to decimate the samples of the remaining phases, therebyperforming partial correlation on each sample. More specifically, theinput signal is decimated at a rate of 1/N for each sampling phase, soas to pass through each partial correlator.

For example, when the input signal is oversampled to 2 times (i.e., whenN=2), this indicates that two samples are included in one signal. Inthis case, two partial correlators are required, and each 1/N decimatorbecomes a 1/2 decimator. At this point, the 1/N decimator of the firstpartial correlator 811 decimates (or removes), among the input samples,the samples located in-between symbol places (or positions). Then, thecorresponding 1/N decimator outputs the decimated sample to the partialcorrelator. Furthermore, the 1 sample delay of the second partialcorrelator 812 delays the input sample by 1 sample (i.e., performs a 1sample delay on the input sample) and outputs the delayed input sampleto the 1/N decimator. Subsequently, among the samples inputted from the1 sample delay, the 1/N decimator of the second partial correlator 812decimates (or removes) the samples located in-between symbol places (orpositions). Thereafter, the corresponding 1/N decimator outputs thedecimated sample to the partial correlator.

After each predetermined period of the symbol, each of the partialcorrelators outputs a correlation value and an estimation value of thefrequency offset estimated at that particular moment to the known dataplace detector and frequency offset decider 820. The known data placedetector and frequency offset decider 820 stores the output of thepartial correlators corresponding to each sampling phase during an datagroup cycle or a pre-decided cycle. Thereafter, the known data placedetector and frequency offset decider 820 decides a position (or place)corresponding to the highest correlation value, among the stored values,as the place (or position) for receiving the known data. Simultaneously,the known data place detector and frequency offset decider 820 finallydecides the estimation value of the frequency offset estimated at themoment corresponding to the highest correlation value as the coarsefrequency offset value of the receiving system.

FIG. 12 illustrates a block diagram showing the structure of one of thepartial correlators shown in FIG. 11. During the step of detecting knowndata, since a frequency offset is included in the received signal, eachpartial correlator divides the known data, which is known according toan agreement between the transmitting system and the receiving system,to K number of parts each having an L symbol length, thereby correlatingeach divided part with the corresponding part of the received signal. Inorder to do so, each partial correlator includes K number of phase andsize detector 911 to 91K each formed in parallel, an adder 920, and acoarse frequency offset estimator 930.

The first phase and size detector 911 includes an L symbol buffer 911-2,a multiplier 911-3, an accumulator 911-4, and a squarer 911-5. Herein,the first phase and size detector 911 calculates the correlation valueof the known data having a first L symbol length among the K number ofsections. Also, the second phase and size detector 912 includes an Lsymbol delay 912-1, an L symbol buffer 912-2, a multiplier 912-3, anaccumulator 912-4, and a squarer 912-5. Herein, the second phase andsize detector 912 calculates the correlation value of the known datahaving a second L symbol length among the K number of sections. Finally,the N^(th) phase and size detector 91K includes a (K-1)L symbol delay91K-1, an L symbol buffer 91K-2, a multiplier 91K-3, an accumulator91K-4, and a squarer 91K-5. Herein, the N^(th) phase and size detector91K calculates the correlation value of the known data having an N^(th)L symbol length among the K number of sections.

Referring to FIG. 12, {P₀, P₁, . . . , P_(KL-1)} each being multipliedwith the received signal in the multiplier represents the referenceknown data sequence known by both the transmitting system and thereceiving system. And, * represents a complex conjugate. For example, inthe first phase and size detector 911, the signal outputted from the 1/Ndecimator of the first partial correlator 811, shown in FIG. 11, istemporarily stored in the L symbol buffer 911-2 of the first phase andsize detector 911 and then inputted to the multiplier 911-3. Themultiplier 911-3 multiplies the output of the L symbol buffer 911-2 withthe complex conjugate of the known data parts P₀, P₁, . . . P_(KL-1),each having a first L symbol length among the known K number ofsections. Then, the multiplied result is outputted to the accumulator911-4. During the L symbol period, the accumulator 911-4 accumulates theoutput of the multiplier 911-3 and, then, outputs the accumulated valueto the squarer 911-5 and the coarse frequency offset estimator 930. Theoutput of the accumulator 911-4 is a correlation value having a phaseand a size. Accordingly, the squarer 911-5 calculates an absolute valueof the output of the multiplier 911-4 and squares the calculatedabsolute value, thereby obtaining the size of the correlation value. Theobtained size is then inputted to the adder 920.

The adder 920 adds the output of the squarers corresponding to each sizeand phase detector 911 to 91K. Then, the adder 920 outputs the addedresult to the known data place detector and frequency offset decider820. Also, the coarse frequency offset estimator 930 receives the outputof the accumulator corresponding to each size and phase detector 911 to91K, so as to estimate the coarse frequency offset at each correspondingsampling phase. Thereafter, the coarse frequency offset estimator 930outputs the estimated offset value to the known data place detector andfrequency offset decider 820. When the K number of inputs that areoutputted from the accumulator of each phase and size detector 911 to91K are each referred to as {Z₀, Z₁, . . . , Z_(K-1)}, the output of thecoarse frequency offset estimator 930 may be obtained by using Equation1 shown below.

$\begin{matrix}{\omega_{0} = {\frac{1}{L}\arg\left\{ {\sum\limits_{n = 1}^{K - 1}\;{\left( \frac{Z_{n}}{Z_{n}} \right)\;\left( \frac{Z_{n - 1}}{Z_{n - 1}} \right)^{*}}} \right\}}} & {{Equation}\mspace{14mu} 1}\end{matrix}$

The known data place detector and frequency offset decider 820 storesthe output of the partial correlator corresponding to each samplingphase during an data group cycle or a pre-decided cycle. Then, among thestored correlation values, the known data place detector and frequencyoffset decider 820 decides the place (or position) corresponding to thehighest correlation value as the place for receiving the known data.Furthermore, the known data place detector and frequency offset decider820 decides the estimated value of the frequency offset taken (orestimated) at the point of the highest correlation value as the coarsefrequency offset value of the receiving system. For example, if theoutput of the partial correlator corresponding to the second partialcorrelator 812 is the highest value, the place corresponding to thehighest value is decided as the known data place. Thereafter, the coarsefrequency offset estimated by the second partial correlator 812 isdecided as the final coarse frequency offset, which is then outputted tothe selector 703.

FIG. 13 illustrates a block diagram showing the structure of a digitalbroadcast receiving system according to an embodiment of the presentinvention. Referring to FIG. 13, the digital broadcast receiving systemincludes a tuner 1001, a demodulating unit 1002, a demultiplexer 1003,an audio decoder 1004, a video decoder 1005, a native TV applicationmanager 1006, a channel manager 1007, a channel map 1008, a first memory1009, a data decoder 1010, a second memory 1011, a system manager 1012,a data broadcasting application manager 1013, a storage controller 1014,and a third memory 1015. Herein, the third memory 1015 is a mass storagedevice, such as a hard disk drive (HDD) or a memory chip. The tuner 1001tunes a frequency of a specific channel through any one of an antenna,cable, and satellite. Then, the tuner 1001 down-converts the tunedfrequency to an intermediate frequency (IF), which is then outputted tothe demodulating unit 1002. At this point, the tuner 1001 is controlledby the channel manager 1007. Additionally, the result and strength ofthe broadcast signal of the tuned channel are also reported to thechannel manager 1007. The data that are being received by the frequencyof the tuned specific channel include main data, enhanced data, andtable data for decoding the main data and enhanced data.

In the embodiment of the present invention, examples of the enhanceddata may include data provided for data service, such as Javaapplication data, HTML application data, XML data, and so on. The dataprovided for such data services may correspond either to a Java classfile for the Java application, or to a directory file designatingpositions (or locations) of such files. Furthermore, such data may alsocorrespond to an audio file and/or a video file used in eachapplication. The data services may include weather forecast services,traffic information services, stock information services, servicesproviding information quiz programs providing audience participationservices, real time poll, user interactive education programs, gamingservices, services providing information on soap opera (or TV series)synopsis, characters, original sound track, filing sites, servicesproviding information on past sports matches, profiles andaccomplishments of sports players, product information and productordering services, services providing information on broadcast programsby media type, airing time, subject, and so on. The types of dataservices described above are only exemplary and are not limited only tothe examples given herein. Furthermore, depending upon the embodiment ofthe present invention, the enhanced data may correspond to meta data.For example, the meta data use the XML application so as to betransmitted through a DSM-CC protocol.

The demodulating unit 1002 performs VSB-demodulation and channelequalization on the signal being outputted from the tuner 1001, therebyidentifying the main data and the enhanced data. Thereafter, theidentified main data and enhanced data are outputted in TS packet units.Example of the demodulating unit 1002 is shown in FIG. 9. Thedemodulating unit shown in FIG. 9 is merely exemplary and the scope ofthe present invention is not limited to the examples set forth herein.In the embodiment given as an example of the present invention, only theenhanced data packet outputted from the demodulating unit 1002 isinputted to the demultiplexer 1003. In this case, the main data packetis inputted to another demultiplexer (not shown) that processes maindata packets. Herein, the storage controller 1014 is also connected tothe other demultiplexer in order to store the main data after processingthe main data packets. The demultiplexer of the present invention mayalso be designed to process both enhanced data packets and main datapackets in a single demultiplexer.

The storage controller 1014 is interfaced with the demultipelxer so asto control instant recording, reserved (or pre-programmed) recording,time shift, and so on of the enhanced data and/or main data. Forexample, when one of instant recording, reserved (or pre-programmed)recording, and time shift is set and programmed in the receiving system(or receiver) shown in FIG. 13, the corresponding enhanced data and/ormain data that are inputted to the demultiplexer are stored in the thirdmemory 1015 in accordance with the control of the storage controller1014. The third memory 1015 may be described as a temporary storage areaand/or a permanent storage area. Herein, the temporary storage area isused for the time shifting function, and the permanent storage area isused for a permanent storage of data according to the user's choice (ordecision).

When the data stored in the third memory 1015 need to be reproduced (orplayed), the storage controller 1014 reads the corresponding data storedin the third memory 1015 and outputs the read data to the correspondingdemultiplexer (e.g., the enhanced data are outputted to thedemultiplexer 1003 shown in FIG. 13). At this point, according to theembodiment of the present invention, since the storage capacity of thethird memory 1015 is limited, the compression encoded enhanced dataand/or main data that are being inputted are directly stored in thethird memory 1015 without any modification for the efficiency of thestorage capacity. In this case, depending upon the reproduction (orreading) command, the data read from the third memory 1015 pass troughthe demultiplexer so as to be inputted to the corresponding decoder,thereby being restored to the initial state.

The storage controller 1014 may control the reproduction (or play),fast-forward, rewind, slow motion, instant replay functions of the datathat are already stored in the third memory 1015 or presently beingbuffered. Herein, the instant replay function corresponds to repeatedlyviewing scenes that the viewer (or user) wishes to view once again. Theinstant replay function may be performed on stored data and also on datathat are currently being received in real time by associating theinstant replay function with the time shift function. If the data beinginputted correspond to the analog format, for example, if thetransmission mode is NTSC, PAL, and so on, the storage controller 1014compression encodes the inputted data and stored the compression-encodeddata to the third memory 1015. In order to do so, the storage controller1014 may include an encoder, wherein the encoder may be embodied as oneof software, middleware, and hardware. Herein, an MPEG encoder may beused as the encoder according to an embodiment of the present invention.The encoder may also be provided outside of the storage controller 1014.

Meanwhile, in order to prevent illegal duplication (or copies) of theinput data being stored in the third memory 1015, the storage controller1014 scrambles the input data and stores the scrambled data in the thirdmemory 1015. Accordingly, the storage controller 1014 may include ascramble algorithm for scrambling the data stored in the third memory1015 and a descramble algorithm for descrambling the data read from thethird memory 1015. Herein, the definition of scramble includesencryption, and the definition of descramble includes decryption. Thescramble method may include using an arbitrary key (e.g., control word)to modify a desired set of data, and also a method of mixing signals.

Meanwhile, the demultiplexer 1003 receives the real-time data outputtedfrom the demodulating unit 1002 or the data read from the third memory1015 and demultiplexes the received data. In the example given in thepresent invention, the demultiplexer 1003 performs demultiplexing on theenhanced data packet. Therefore, in the present invention, the receivingand processing of the enhanced data will be described in detail. Itshould also be noted that a detailed description of the processing ofthe main data will be omitted for simplicity starting from thedescription of the demultiplexer 1003 and the subsequent elements.

The demultiplexer 1003 demultiplexes enhanced data and program specificinformation/program and system information protocol (PSI/PSIP) tablesfrom the enhanced data packet inputted in accordance with the control ofthe data decoder 1010. Thereafter, the demultiplexed enhanced data andPSI/PSIP tables are outputted to the data decoder 1010 in a sectionformat. In order to extract the enhanced data from the channel throughwhich enhanced data are transmitted and to decode the extracted enhanceddata, system information is required. Such system information may alsobe referred to as service information. The system information mayinclude channel information, event information, etc. In the embodimentof the present invention, the PSI/PSIP tables are applied as the systeminformation. However, the present invention is not limited to theexample set forth herein. More specifically, regardless of the name, anyprotocol transmitting system information in a table format may beapplied in the present invention.

The PSI table is an MPEG-2 system standard defined for identifying thechannels and the programs. The PSIP table is an advanced televisionsystems committee (ATSC) standard that can identify the channels and theprograms. The PSI table may include a program association table (PAT), aconditional access table (CAT), a program map table (PMT), and a networkinformation table (NIT). Herein, the PAT corresponds to specialinformation that is transmitted by a data packet having a PID of ‘0’.The PAT transmits PID information of the PMT and PID information of theNIT corresponding to each program. The CAT transmits information on apaid broadcast system used by the transmitting system. The PMT transmitsPID information of a transport stream (TS) packet, in which programidentification numbers and individual bit sequences of video and audiodata configuring the corresponding program are transmitted, and the PIDinformation, in which PCR is transmitted. The NIT transmits informationof the actual transmission network.

The PSIP table may include a virtual channel table (VCT), a system timetable (STT), a rating region table (RRT), an extended text table (ETT),a direct channel change table (DCCT), an event information table (EIT),and a master guide table (MGT). The VCT transmits information on virtualchannels, such as channel information for selecting channels andinformation such as packet identification (PID) numbers for receivingthe audio and/or video data. More specifically, when the VCT is parsed,the PID of the audio/video data of the broadcast program may be known.Herein, the corresponding audio/video data are transmitted within thechannel along with the channel name and the channel number. The STTtransmits information on the current data and timing information. TheRRT transmits information on region and consultation organs for programratings. The ETT transmits additional description of a specific channeland broadcast program. The EIT transmits information on virtual channelevents (e.g., program title, program start time, etc.). The DCCT/DCCSCTtransmits information associated with automatic (or direct) channelchange. And, the MGT transmits the versions and PID information of theabove-mentioned tables included in the PSIP.

Each of the above-described tables included in the PSI/PSIP isconfigured of a basic unit referred to as a “section”, and a combinationof one or more sections forms a table. For example, the VCT may bedivided into 256 sections. Herein, one section may include a pluralityof virtual channel information. However, a single set of virtual channelinformation is not divided into two or more sections. At this point, thereceiving system may parse and decode the data for the data service thatare transmitting by using only the tables included in the PSI, or onlythe tables included in the PSIP, or a combination of tables included inboth the PSI and the PSIP. In order to parse and decode the data for thedata service, at least one of the PAT and PMT included in the PSI, andthe VCT included in the PSIP is required. For example, the PAT mayinclude the system information for transmitting the data correspondingto the data service, and the PID of the PMT corresponding to the dataservice data (or program number). The PMT may include the PID of the TSpacket used for transmitting the data service data. The VCT may includeinformation on the virtual channel for transmitting the data servicedata, and the PID of the TS packet for transmitting the data servicedata.

Meanwhile, depending upon the embodiment of the present invention, aDVB-SI may be applied instead of the PSIP. The DVB-SI may include anetwork information table (NIT), a service description table (SDT), anevent information table (ETT), and a time and data table (TDT), TheDVB-SI may be used in combination with the above-described PSI. Herein,the NIT divides the services corresponding to particular networkproviders by specific groups. The NIT includes all tuning informationthat is used during the IRD set-up. The NIT may be used for informing ornotifying any change in the tuning information. The SDT includes theservice name and different parameters associated with each servicecorresponding to a particular MPEG multiplex. The EIT is used fortransmitting information associated with all events occurring in theMPEG multiplex. The EIT includes information on the current transmissionand also includes information selectively containing differenttransmission streams that may be received by the IRD. And, the TDT isused for updating the clock included in the IRD.

Furthermore, three selective SI tables (i.e., a bouquet associate table(BAT), a running status table (RST), and a stuffing table (ST)) may alsobe included. More specifically, the bouquet associate table (BAT)provides a service grouping method enabling the IRD to provide servicesto the viewers. Each specific service may belong to at least one‘bouquet’ unit. A running status table (RST) section is used forpromptly and instantly updating at least one event execution status. Theexecution status section is transmitted only once at the changing pointof the event status. Other SI tables are generally transmitted severaltimes. The stuffing table (ST) may be used for replacing or discarding asubsidiary table or the entire SI tables.

In the present invention, the enhanced data included in the payloadwithin the TS packet consist of a digital storage media-command andcontrol (DSM-CC) section format. However, the TS packet including thedata service data may correspond either to a packetized elementarystream (PES) type or to a section type. More specifically, either thePES type data service data configure the TS packet, or the section typedata service data configure the TS packet. The TS packet configured ofthe section type data will be given as the example of the presentinvention. At this point, the data service data are includes in thedigital storage media-command and control (DSM-CC) section. Herein, theDSM-CC section is then configured of a 188-byte unit TS packet.

Furthermore, the packet identification of the TS packet configuring theDSM-CC section is included in a data service table (DST). Whentransmitting the DST, ‘0x95’ is assigned as the value of a stream typefield included in the service location descriptor of the PMT or the VCT.More specifically, when the PMT or VCT stream_type field value is‘0x95’, the receiving system may acknowledge that data broadcastingincluding enhanced data (i.e., the enhanced data) is being received. Atthis point, the enhanced data may be transmitted by a data carouselmethod. The data carousel method corresponds to repeatedly transmittingidentical data on a regular basis.

At this point, according to the control of the data decoder 1010, thedemultiplexer 1003 performs section filtering, thereby discardingrepetitive sections and outputting only the non-repetitive sections tothe data decoder 1010. The demultiplexer 1003 may also output only thesections configuring desired tables (e.g., VCT) to the data decoder 1010by section filtering. Herein, the VCT may include a specific descriptorfor the enhanced data. However, the present invention does not excludethe possibilities of the enhanced data being included in other tables,such as the PMT. The section filtering method may include a method ofverifying the PID of a table defined by the MGT, such as the VCT, priorto performing the section filtering process. Alternatively, the sectionfiltering method may also include a method of directly performing thesection filtering process without verifying the MGT, when the VCTincludes a fixed PID (i.e., a base PID). At this point, thedemultiplexer 1003 performs the section filtering process by referringto a table_id field, a version_number field, a section_number field,etc.

As described above, the method of defining the PID of the VCT broadlyincludes two different methods. Herein, the PID of the VCT is a packetidentifier required for identifying the VCT from other tables. The firstmethod consists of setting the PID of the VCT so that it is dependent tothe MGT. In this case, the receiving system cannot directly verify theVCT among the many PSI and/or PSIP tables. Instead, the receiving systemmust check the PID defined in the MGT in order to read the VCT. Herein,the MGT defines the PID, size, version number, and so on, of diversetables. The second method consists of setting the PID of the VCT so thatthe PID is given a base PID value (or a fixed PID value), thereby beingindependent from the MGT. In this case, unlike in the first method, theVCT according to the present invention may be identified without havingto verify every single PID included in the MGT. Evidently, an agreementon the base PID must be previously made between the transmitting systemand the receiving system.

Meanwhile, in the embodiment of the present invention, the demultiplexer1003 may output only an application information table (AIT) to the datadecoder 1010 by section filtering. The AIT includes information on anapplication being operated in the receiving system for the data service.The AIT may also be referred to as an XAIT, and an AMT. Therefore, anytable including application information may correspond to the followingdescription. When the AIT is transmitted, a value of ‘0x05’ may beassigned to a stream_type field of the PMT. The AIT may includeapplication information, such as application name, application version,application priority, application ID, application status (i.e.,auto-start, user-specific settings, kill, etc.), application type (i.e.,Java or HTML), position (or location) of stream including applicationclass and data files, application platform directory, and location ofapplication icon.

In the method for detecting application information for the data serviceby using the AIT, component_tag, original_network_id,transport_stream_id, and service_id fields may be used for detecting theapplication information. The component_tag field designates anelementary stream carrying a DSI of a corresponding object carousel. Theoriginal_network_id field indicates a DVB-SI original_network_id of theTS providing transport connection. The transport_stream_id fieldindicates the MPEG TS of the TS providing transport connection, and theservice_id field indicates the DVB-SI of the service providing transportconnection. Information on a specific channel may be obtained by usingthe original_network_id field, the transport_stream_id field, and theservice_id field. The data service data, such as the application data,detected by using the above-described method may be stored in the secondmemory 1011 by the data decoder 1010.

The data decoder 1010 parses the DSM-CC section configuring thedemultiplexed enhanced data. Then, the enhanced data corresponding tothe parsed result are stored as a database in the second memory 1011.The data decoder 1010 groups a plurality of sections having the sametable identification (table_id) so as to configure a table, which isthen parsed. Thereafter, the parsed result is stored as a database inthe second memory 1011. At this point, by parsing data and/or sections,the data decoder 1010 reads all of the remaining actual section datathat are not section-filtered by the demultiplexer 1003. Then, the datadecoder 1010 stores the read data to the second memory 1011. The secondmemory 1011 corresponds to a table and data carousel database storingsystem information parsed from tables and enhanced data parsed from theDSM-CC section. Herein, a table id field, a section_number field, and alast_section_number field included in the table may be used to indicatewhether the corresponding table is configured of a single section or aplurality of sections. For example, TS packets having the PID of the VCTare grouped to form a section, and sections having table identifiersallocated to the VCT are grouped to form the VCT,

When the VCT is parsed, information on the virtual channel to whichenhanced data are transmitted may be obtained. The obtained applicationidentification information, service component identificationinformation, and service information corresponding to the data servicemay either be stored in the second memory 1011 or be outputted to thedata broadcasting application manager 1013. In addition, reference maybe made to the application identification information, service componentidentification information, and service information in order to decodethe data service data. Alternatively, such information may also preparethe operation of the application program for the data service.Furthermore, the data decoder 1010 controls the demultiplexing of thesystem information table, which corresponds to the information tableassociated with the channel and events. Thereafter, an A.V PID list maybe transmitted to the channel manager 1007.

The channel manager 1007 may refer to the channel map 1008 in order totransmit a request for receiving system-related information data to thedata decoder 1010, thereby receiving the corresponding result. Inaddition, the channel manager 1007 may also control the channel tuningof the tuner 1001. Furthermore, the channel manager 1007 may directlycontrol the demultiplexer 1003, so as to set up the A/V PID, therebycontrolling the audio decoder 1004 and the video decoder 1005. The audiodecoder 1004 and the video decoder 1005 may respectively decode andoutput the audio data and video data demultiplexed from the main datapacket. Alternatively, the audio decoder 1004 and the video decoder 1005may respectively decode and output the audio data and video datademultiplexed from the enhanced data packet. Meanwhile, when theenhanced data include data service data, and also audio data and videodata, it is apparent that the audio data and video data demultiplexed bythe demultiplexer 1003 are respectively decoded by the audio decoder1004 and the video decoder 1005. For example, an audio-coding (AC)-3decoding algorithm may be applied to the audio decoder 1004, and aMPEG-2 decoding algorithm may be applied to the video decoder 1005.

Meanwhile, the native TV application manager 1006 operates a nativeapplication program stored in the first memory 1009, thereby performinggeneral functions such as channel change. The native application programrefers to software stored in the receiving system upon shipping of theproduct. More specifically, when a user request (or command) istransmitted to the receiving system through a user interface (UI), thenative TV application manger 1006 displays the user request on a screenthrough a graphic user interface (GUI), thereby responding to the user'srequest. The user interface receives the user request through an inputdevice, such as a remote controller, a key pad, a jog controller, an atouch-screen provided on the screen, and then outputs the received userrequest to the native TV application manager 1006 and the databroadcasting application manager 1013. Furthermore, the native TVapplication manager 1006 controls the channel manager 1007, therebycontrolling channel-associated, such as the management of the channelmap 1008, and controlling the data decoder 1010. The native TVapplication manager 1006 also controls the GUI of the overall receivingsystem, thereby storing the user request and status of the receivingsystem in the first memory 1009 and restoring the stored information.

The channel manager 1007 controls the tuner 1001 and the data decoder1010, so as to managing the channel map 1008 so that it can respond tothe channel request made by the user. More specifically, channel manager1007 sends a request to the data decoder 1010 so that the tablesassociated with the channels that are to be tuned are parsed. Theresults of the parsed tables are reported to the channel manager 1007 bythe data decoder 1010. Thereafter, based on the parsed results, thechannel manager 1007 updates the channel map 1008 and sets up a PID inthe demultiplexer 1003 for demultiplexing the tables associated with thedata service data from the enhanced data.

The system manager 1012 controls the booting of the receiving system byturning the power on or off. Then, the system manager 1012 stores ROMimages (including downloaded software images) in the first memory 1009.More specifically, the first memory 1009 stores management programs suchas operating system (OS) programs required for managing the receivingsystem and also application program executing data service functions.The application program is a program processing the data service datastored in the second memory 1011 so as to provide the user with the dataservice. If the data service data are stored in the second memory 1011,the corresponding data service data are processed by the above-describedapplication program or by other application programs, thereby beingprovided to the user. The management program and application programstored in the first memory 1009 may be updated or corrected to a newlydownloaded program. Furthermore, the storage of the stored managementprogram and application program is maintained without being deleted evenif the power of the system is shut down. Therefore, when the power issupplied the programs may be executed without having to be newlydownloaded once again.

The application program for providing data service according to thepresent invention may either be initially stored in the first memory1009 upon the shipping of the receiving system, or be stored in thefirst 1009 after being downloaded. The application program for the dataservice (i.e., the data service providing application program) stored inthe first memory 1009 may also be deleted, updated, and corrected.Furthermore, the data service providing application program may bedownloaded and executed along with the data service data each time thedata service data are being received.

When a data service request is transmitted through the user interface,the data broadcasting application manager 1013 operates thecorresponding application program stored in the first memory 1009 so asto process the requested data, thereby providing the user with therequested data service. And, in order to provide such data service, thedata broadcasting application manager 1013 supports the graphic userinterface (GUI). Herein, the data service may be provided in the form oftext (or short message service (SMS)), voice message, still image, andmoving image. The data broadcasting application manager 1013 may beprovided with a platform for executing the application program stored inthe first memory 1009. The platform may be, for example, a Java virtualmachine for executing the Java program. Hereinafter, an example of thedata broadcasting application manager 1013 executing the data serviceproviding application program stored in the first memory 1009, so as toprocess the data service data stored in the second memory 1011, therebyproviding the user with the corresponding data service will now bedescribed in detail.

Assuming that the data service corresponds to a traffic informationservice, the data service according to the present invention is providedto the user of a receiving system that is not equipped with anelectronic map and/or a GPS system in the form of at least one of a text(or short message service (SMS)), a voice message, a graphic message, astill image, and a moving image. In this case, is a GPS module ismounted on the receiving system shown in FIG. 13, the GPS modulereceives satellite signals transmitted from a plurality of low earthorbit satellites and extracts the current position (or location)information (e.g., longitude, latitude, altitude), thereby outputtingthe extracted information to the data broadcasting application manager1013.

At this point, it is assumed that the electronic map includinginformation on each link and nod and other diverse graphic informationare stored in one of the second memory 1011, the first memory 1009, andanother memory that is not shown. More specifically, according to therequest made by the data broadcasting application manager 1013, the dataservice data stored in the second memory 1011 are read and inputted tothe data broadcasting application manager 1013. The data broadcastingapplication manager 1013 translates (or deciphers) the data service dataread from the second memory 1011, thereby extracting the necessaryinformation according to the contents of the message and/or a controlsignal.

FIG. 14 illustrates a block diagram showing the structure of a digitalbroadcast (or television) receiving system according to anotherembodiment of the present invention. Referring to FIG. 14, the digitalbroadcast receiving system includes a tuner 2001, a demodulating unit2002, a demultiplexer 2003, a first descrambler 2004, an audio decoder2005, a video decoder 2006, a second descrambler 2007, an authenticationunit 2008, a native TV application manager 2009, a channel manager 2010,a channel map 2011, a first memory 2012, a data decoder 2013, a secondmemory 2014, a system manager 2015, a data broadcasting applicationmanager 2016, a storage controller 2017, a third memory 2018, and atelecommunication module 2019. Herein, the third memory 2018 is a massstorage device, such as a hard disk drive (HDD) or a memory chip. Also,during the description of the digital broadcast (or television or DTV)receiving system shown in FIG. 14, the components that are identical tothose of the digital broadcast receiving system of FIG. 13 will beomitted for simplicity.

As described above, in order to provide services for preventing illegalduplication (or copies) or illegal viewing of the enhanced data and/ormain data that are transmitted by using a broadcast network, and toprovide paid broadcast services, the transmitting system may generallyscramble and transmit the broadcast contents. Therefore, the receivingsystem needs to descramble the scrambled broadcast contents in order toprovide the user with the proper broadcast contents. Furthermore, thereceiving system may generally be processed with an authenticationprocess with an authentication means before the descrambling process.Hereinafter, the receiving system including an authentication means anda descrambling means according to an embodiment of the present inventionwill now be described in detail.

According to the present invention, the receiving system may be providedwith a descrambling means receiving scrambled broadcasting contents andan authentication means authenticating (or verifying) whether thereceiving system is entitled to receive the descrambled contents.Hereinafter, the descrambling means will be referred to as first andsecond descramblers 2004 and 2007, and the authentication means will bereferred to as an authentication unit 2008. Such naming of thecorresponding components is merely exemplary and is not limited to theterms suggested in the description of the present invention. Forexample, the units may also be referred to as a decryptor. Although FIG.14 illustrates an example of the descramblers 2004 and 2007 and theauthentication unit 2008 being provided inside the receiving system,each of the descramblers 2004 and 2007 and the authentication unit 2008may also be separately provided in an internal or external module.Herein, the module may include a slot type, such as a SD or CF memory, amemory stick type, a USB type, and so on, and may be detachably fixed tothe receiving system.

As described above, when the authentication process is performedsuccessfully by the authentication unit 2008, the scrambled broadcastingcontents are descrambled by the descramblers 2004 and 2007, therebybeing provided to the user. At this point, a variety of theauthentication method and descrambling method may be used herein.However, an agreement on each corresponding method should be madebetween the receiving system and the transmitting system. Hereinafter,the authentication and descrambling methods will now be described, andthe description of identical components or process steps will be omittedfor simplicity.

The receiving system including the authentication unit 2008 and thedescramblers 2004 and 2007 will now be described in detail. Thereceiving system receives the scrambled broadcasting contents throughthe tuner 2001 and the demodulating unit 2002. Then, the system manager2015 decides whether the received broadcasting contents have beenscrambled. Herein, the demodulating unit 2002 may be included as ademodulating unit according to embodiments of the present invention asdescribed in FIG. 9. However, the present invention is not limited tothe examples given in the description set forth herein. If the systemmanager 2015 decides that the received broadcasting contents have beenscrambled, then the system manager 2015 controls the system to operatethe authentication unit 2008. As described above, the authenticationunit 2008 performs an authentication process in order to decide whetherthe receiving system according to the present invention corresponds to alegitimate host entitled to receive the paid broadcasting service.Herein, the authentication process may vary in accordance with theauthentication methods.

For example, the authentication unit 2008 may perform the authenticationprocess by comparing an IP address of an IP datagram within the receivedbroadcasting contents with a specific address of a corresponding host.At this point, the specific address of the corresponding receivingsystem (or host) may be a MAC address. More specifically, theauthentication unit 2008 may extract the IP address from thedecapsulated IP datagram, thereby obtaining the receiving systeminformation that is mapped with the IP address. At this point, thereceiving system should be provided, in advance, with information (e.g.,a table format) that can map the IP address and the receiving systeminformation. Accordingly, the authentication unit 2008 performs theauthentication process by determining the conformity between the addressof the corresponding receiving system and the system information of thereceiving system that is mapped with the IP address. In other words, ifthe authentication unit 2008 determines that the two types ofinformation conform to one another, then the authentication unit 2008determines that the receiving system is entitled to receive thecorresponding broadcasting contents.

In another example, standardized identification information is definedin advance by the receiving system and the transmitting system. Then,the identification information of the receiving system requesting thepaid broadcasting service is transmitted by the transmitting system.Thereafter, the receiving system determines whether the receivedidentification information conforms with its own unique identificationnumber, so as to perform the authentication process. More specifically,the transmitting system creates a database for storing theidentification information (or number) of the receiving systemrequesting the paid broadcasting service. Then, if the correspondingbroadcasting contents are scrambled, the transmitting system includesthe identification information in the EMM, which is then transmitted tothe receiving system.

If the corresponding broadcasting contents are scrambled, messages(e.g., entitlement control message (ECM), entitlement management message(EMM)), such as the CAS information, mode information, message positioninformation, that are applied to the scrambling of the broadcastingcontents are transmitted through a corresponding data header or antherdata packet. The ECM may include a control word (CW) used for scramblingthe broadcasting contents. At this point, the control word may beencoded with an authentication key. The EMM may include anauthentication key and entitlement information of the correspondingdata. Herein, the authentication key may be encoded with a receivingsystem-specific distribution key. In other words, assuming that theenhanced data are scrambled by using the control word, and that theauthentication information and the descrambling information aretransmitted from the transmitting system, the transmitting systemencodes the CW with the authentication key and, then, includes theencoded CW in the entitlement control message (ECM), which is thentransmitted to the receiving system. Furthermore, the transmittingsystem includes the authentication key used for encoding the CW and theentitlement to receive data (or services) of the receiving system (i.e.,a standardized serial number of the receiving system that is entitled toreceive the corresponding broadcasting service or data) in theentitlement management message (EMM), which is then transmitted to thereceiving system.

Accordingly, the authentication unit 2008 of the receiving systemextracts the identification information of the receiving system and theidentification information included in the EMM of the broadcastingservice that is being received. Then, the authentication unit 2008determines whether the identification information conform to each other,so as to perform the authentication process. More specifically, if theauthentication unit 2008 determines that the information conform to eachother, then the authentication unit 2008 eventually determines that thereceiving system is entitled to receive the request broadcastingservice.

In yet another example, the authentication unit 2008 of the receivingsystem may be detachably fixed to an external module. In this case, thereceiving system is interfaced with the external module through a commoninterface (CI). In other words, the external module may receive the datascrambled by the receiving system through the common interface, therebyperforming the descrambling process of the received data. Alternatively,the external module may also transmit only the information required forthe descrambling process to the receiving system. The common interfaceis configured on a physical layer and at least one protocol layer.Herein, in consideration of any possible expansion of the protocol layerin a later process, the corresponding protocol layer may be configuredto have at least one layer that can each provide an independentfunction.

The external module may either consist of a memory or card havinginformation on the key used for the scrambling process and otherauthentication information but not including any descrambling function,or consist of a card having the above-mentioned key information andauthentication information and including the descrambling function. Boththe receiving system and the external module should be authenticated inorder to provide the user with the paid broadcasting service provided(or transmitted) from the transmitting system. Therefore, thetransmitting system can only provide the corresponding paid broadcastingservice to the authenticated pair of receiving system and externalmodule.

Additionally, an authentication process should also be performed betweenthe receiving system and the external module through the commoninterface. More specifically, the module may communicate with the systemmanager 2015 included in the receiving system through the commoninterface, thereby authenticating the receiving system. Alternatively,the receiving system may authenticate the module through the commoninterface. Furthermore, during the authentication process, the modulemay extract the unique ID of the receiving system and its own unique IDand transmit the extracted IDs to the transmitting system. Thus, thetransmitting system may use the transmitted ID values as informationdetermining whether to start the requested service or as paymentinformation. Whenever necessary, the system manager 2015 transmits thepayment information to the remote transmitting system through thetelecommunication module 2019.

The authentication unit 2008 authenticates the corresponding receivingsystem and/or the external module. Then, if the authentication processis successfully completed, the authentication unit 2008 certifies thecorresponding receiving system and/or the external module as alegitimate system and/or module entitled to receive the requested paidbroadcasting service. In addition, the authentication unit 2008 may alsoreceive authentication-associated information from a mobiletelecommunications service provider to which the user of the receivingsystem is subscribed, instead of the transmitting system providing therequested broadcasting service. In this case, theauthentication-association information may either be scrambled by thetransmitting system providing the broadcasting service and, then,transmitted to the user through the mobile telecommunications serviceprovider, or be directly scrambled and transmitted by the mobiletelecommunications service provider. Once the authentication process issuccessfully completed by the authentication unit 2008, the receivingsystem may descramble the scrambled broadcasting contents received fromthe transmitting system. At this point, the descrambling process isperformed by the first and second descramblers 2004 and 2007. Herein,the first and second descramblers 2004 and 2007 may be included in aninternal module or an external module of the receiving system.

The receiving system is also provided with a common interface forcommunicating with the external module including the first and seconddescramblers 2004 and 2007, so as to perform the descrambling process.More specifically, the first and second descramblers 2004 and 2007 maybe included in the module or in the receiving system in the form ofhardware, middleware or software. Herein, the descramblers 2004 and 2007may be included in any one of or both of the module and the receivingsystem. If the first and second descramblers 2004 and 2007 are providedinside the receiving system, it is advantageous to have the transmittingsystem (i.e., at least any one of a service provider and a broadcaststation) scramble the corresponding data using the same scramblingmethod.

Alternatively, if the first and second descramblers 2004 and 2007 areprovided in the external module, it is advantageous to have eachtransmitting system scramble the corresponding data using differentscrambling methods. In this case, the receiving system is not requiredto be provided with the descrambling algorithm corresponding to eachtransmitting system. Therefore, the structure and size of receivingsystem may be simplified and more compact. Accordingly, in this case,the external module itself may be able to provide CA functions, whichare uniquely and only provided by each transmitting systems, andfunctions related to each service that is to be provided to the user.The common interface enables the various external modules and the systemmanager 2015, which is included in the receiving system, to communicatewith one another by a single communication method. Furthermore, sincethe receiving system may be operated by being connected with at leastone or more modules providing different services, the receiving systemmay be connected to a plurality of modules and controllers.

In order to maintain successful communication between the receivingsystem and the external module, the common interface protocol includes afunction of periodically checking the status of the oppositecorrespondent. By using this function, the receiving system and theexternal module is capable of managing the status of each oppositecorrespondent. This function also reports the user or the transmittingsystem of any malfunction that may occur in any one of the receivingsystem and the external module and attempts the recovery of themalfunction.

In yet another example, the authentication process may be performedthrough software. More specifically, when a memory card having CASsoftware downloaded, for example, and stored therein in advanced isinserted in the receiving system, the receiving system receives andloads the CAS software from the memory card so as to perform theauthentication process. In this example, the CAS software is read outfrom the memory card and stored in the first memory 2012 of thereceiving system. Thereafter, the CAS software is operated in thereceiving system as an application program. According to an embodimentof the present invention, the CAS software is mounted on (or stored) ina middleware platform and, then executed. A Java middleware will begiven as an example of the middleware included in the present invention.Herein, the CAS software should at least include information requiredfor the authentication process and also information required for thedescrambling process.

Therefore, the authentication unit 2008 performs authenticationprocesses between the transmitting system and the receiving system andalso between the receiving system and the memory card. At this point, asdescribed above, the memory card should be entitled to receive thecorresponding data and should include information on a normal receivingsystem that can be authenticated. For example, information on thereceiving system may include a unique number, such as a standardizedserial number of the corresponding receiving system. Accordingly, theauthentication unit 2008 compares the standardized serial numberincluded in the memory card with the unique information of the receivingsystem, thereby performing the authentication process between thereceiving system and the memory card.

If the CAS software is first executed in the Java middleware base, thenthe authentication between the receiving system and the memory card isperformed. For example, when the unique number of the receiving systemstored in the memory card conforms to the unique number of the receivingsystem read from the system manager 2015, then the memory card isverified and determined to be a normal memory card that may be used inthe receiving system. At this point, the CAS software may either beinstalled in the first memory 2012 upon the shipping of the presentinvention, or be downloaded to the first memory 2012 from thetransmitting system or the module or memory card, as described above.Herein, the descrambling function may be operated by the databroadcasting application manger 2016 as an application program.

Thereafter, the CAS software parses the EMM/ECM packets outputted fromthe demultiplexer 2003, so as to verify whether the receiving system isentitled to receive the corresponding data, thereby obtaining theinformation required for descrambling (i.e., the CW) and providing theobtained CW to the descramblers 2004 and 2007. More specifically, theCAS software operating in the Java middleware platform first reads outthe unique (or serial) number of the receiving system from thecorresponding receiving system and compares it with the unique number ofthe receiving system transmitted through the EMM, thereby verifyingwhether the receiving system is entitled to receive the correspondingdata. Once the receiving entitlement of the receiving system isverified, the corresponding broadcasting service information transmittedto the ECM and the entitlement of receiving the correspondingbroadcasting service are used to verify whether the receiving system isentitled to receive the corresponding broadcasting service. Once thereceiving system is verified to be entitled to receive the correspondingbroadcasting service, the authentication key transmitted to the EMM isused to decode (or decipher) the encoded CW, which is transmitted to theECM, thereby transmitting the decoded CW to the descramblers 2004 and2007. Each of the descramblers 2004 and 2007 uses the CW to descramblethe broadcasting service.

Meanwhile, the CAS software stored in the memory card may be expanded inaccordance with the paid service which the broadcast station is toprovide. Additionally, the CAS software may also include otheradditional information other than the information associated with theauthentication and descrambling. Furthermore, the receiving system maydownload the CAS software from the transmitting system so as to upgrade(or update) the CAS software originally stored in the memory card. Asdescribed above, regardless of the type of broadcast receiving system,as long as an external memory interface is provided, the presentinvention may embody a CAS system that can meet the requirements of alltypes of memory card that may be detachably fixed to the receivingsystem. Thus, the present invention may realize maximum performance ofthe receiving system with minimum fabrication cost, wherein thereceiving system may receive paid broadcasting contents such asbroadcast programs, thereby acknowledging and regarding the variety ofthe receiving system. Moreover, since only the minimum applicationprogram interface is required to be embodied in the embodiment of thepresent invention, the fabrication cost may be minimized, therebyeliminating the manufacturer's dependence on CAS manufacturers.Accordingly, fabrication costs of CAS equipments and management systemsmay also be minimized.

Meanwhile, the descramblers 2004 and 2007 may be included in the moduleeither in the form of hardware or in the form of software. In this case,the scrambled data that being received are descrambled by the module andthen demodulated. Also, if the scrambled data that are being receivedare stored in the third memory 2018, the received data may bedescrambled and then stored, or stored in the memory at the point ofbeing received and then descrambled later on prior to being played (orreproduced). Thereafter, in case scramble/descramble algorithms areprovided in the storage controller 2017, the storage controller 2017scrambles the data that are being received once again and then storesthe re-scrambled data to the third memory 2018.

In yet another example, the descrambled broadcasting contents(transmission of which being restricted) are transmitted through thebroadcasting network. Also, information associated with theauthentication and descrambling of data in order to disable thereceiving restrictions of the corresponding data are transmitted and/orreceived through the telecommunications module 2019. Thus, the receivingsystem is able to perform reciprocal (or two-way) communication. Thereceiving system may either transmit data to the telecommunicationmodule within the transmitting system or be provided with the data fromthe telecommunication module within the transmitting system. Herein, thedata correspond to broadcasting data that are desired to be transmittedto or from the transmitting system, and also unique information (i.e.,identification information) such as a serial number of the receivingsystem or MAC address.

The telecommunication module 2019 included in the receiving systemprovides a protocol required for performing reciprocal (or two-way)communication between the receiving system, which does not support thereciprocal communication function, and the telecommunication moduleincluded in the transmitting system. Furthermore, the receiving systemconfigures a protocol data unit (PDU) using a tag-length-value (TLV)coding method including the data that are to be transmitted and theunique information (or ID information). Herein, the tag field includesindexing of the corresponding PDU. The length field includes the lengthof the value field. And, the value field includes the actual data thatare to be transmitted and the unique number (e.g., identificationnumber) of the receiving system.

The receiving system may configure a platform that is equipped with theJava platform and that is operated after downloading the Javaapplication of the transmitting system to the receiving system throughthe network. In this case, a structure of downloading the PDU includingthe tag field arbitrarily defined by the transmitting system from astorage means included in the receiving system and then transmitting thedownloaded PDU to the telecommunication module 2019 may also beconfigured. Also, the PDU may be configured in the Java application ofthe receiving system and then outputted to the telecommunication module2019. The PDU may also be configured by transmitting the tag value, theactual data that are to be transmitted, the unique information of thecorresponding receiving system from the Java application and byperforming the TLV coding process in the receiving system. Thisstructure is advantageous in that the firmware of the receiving systemis not required to be changed even if the data (or application) desiredby the transmitting system is added.

The telecommunication module within the transmitting system eithertransmits the PDU received from the receiving system through a wirelessdata network or configures the data received through the network into aPDU which is transmitted to the host. At this point, when configuringthe PDU that is to be transmitted to the host, the telecommunicationmodule within the transmitting end may include unique information (e.g.,IP address) of the transmitting system which is located in a remotelocation. Additionally, in receiving and transmitting data through thewireless data network, the receiving system may be provided with acommon interface, and also provided with a WAP, CDMA 1x EV-DO, which canbe connected through a mobile telecommunication base station, such asCDMA and GSM, and also provided with a wireless LAN, mobile internet,WiBro, WiMax, which can be connected through an access point. Theabove-described receiving system corresponds to the system that is notequipped with a telecommunication function. However, a receiving systemequipped with telecommunication function does not require thetelecommunication module 2019.

The broadcasting data being transmitted and received through theabove-described wireless data network may include data required forperforming the function of limiting data reception. Meanwhile, thedemultiplexer 2003 receives either the real-time data outputted from thedemodulating unit 2002 or the data read from the third memory 2018,thereby performing demultiplexing. In this embodiment of the presentinvention, the demultiplexer 2003 performs demultiplexing on theenhanced data packet. Similar process steps have already been describedearlier in the description of the present invention. Therefore, adetailed of the process of demultiplexing the enhanced data will beomitted for simplicity.

The first descrambler 2004 receives the demultiplexed signals from thedemultiplexer 2003 and then descrambles the received signals. At thispoint, the first descrambler 2004 may receive the authentication resultreceived from the authentication unit 2008 and other data required forthe descrambling process, so as to perform the descrambling process. Theaudio decoder 2005 and the video decoder 2006 receive the signalsdescrambled by the first descrambler 2004, which are then decoded andoutputted. Alternatively, if the first descrambler 2004 did not performthe descrambling process, then the audio decoder 2005 and the videodecoder 2006 directly decode and output the received signals. In thiscase, the decoded signals are received and then descrambled by thesecond descrambler 2007 and processed accordingly.

As described above, the digital broadcasting systems and methods ofprocessing broadcast data according to the present invention have thefollowing advantages. More specifically, the digital broadcastingreceiving system and method of processing broadcast data according tothe present invention is highly protected against (or resistant to) anyerror that may occur when transmitting supplemental data through achannel. And, the present invention is also highly compatible to theconventional receiving system. Moreover, the present invention may alsoreceive the supplemental data without any error even in channels havingsevere ghost effect and noise.

Additionally, when a known data sequence is inputted to a trellisencoder, by having the transmitting system initialize a memory withinthe trellis encoder and trellis-encode the inputted data, therebyoutputted the processed data, and by having the receiving systemestimate known data information, which is to be used for frequencysynchronization, symbol timing synchronization, frame synchronization,and channel equalization, the receiving performance of the receivingsystem may be enhanced in a situation undergoing severe and frequentchannel changes. Furthermore, the present invention is even moreeffective when applied to mobile and portable receivers, which are alsoliable to a frequent change in channel and which require protection (orresistance) against intense noise.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the inventions. Thus, itis intended that the present invention covers the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

1. A digital television (DTV) receiving system for processing digitalbroadcast data, the DTV receiving system comprising: a tuner forreceiving a broadcast signal including a data group, the data groupcomprising enhanced data, known data sequences, and signalinginformation, wherein at least two of the known data sequences are spaced16 segments apart, wherein an ith segment in the data group has maindata and M consecutive enhanced data bytes, an (i+1)th segment in thedata group has main data and L consecutive enhanced data bytes, and an(i+2)th segment in the data group has main data and K consecutiveenhanced data bytes, and wherein M<L<K; a demodulator for demodulatingthe broadcast signal; an equalizer for compensating a channel distortionof the demodulated broadcast signal using at least one of the known datasequences; an inner decoder for inner decoding the equalized broadcastsignal; and an outer decoder for outer decoding the inner-decodedbroadcast signal.
 2. The DTV receiving system of claim 1, wherein thedata group comprises a plurality of regions, wherein each regioncomprises at least one segment, wherein enhanced data included in atleast a first region of the plurality of regions are received by beingencoded at a coding rate of 1/X, and wherein enhanced data included inat least a second region of the plurality of regions are received bybeing encoded at a coding rate of 1/Y, wherein X≠Y.
 3. The DTV receivingsystem of claim 2, wherein a value of X is equal to 2, and a value of Yis equal to
 4. 4. The DTV receiving system of claim 1, wherein the maindata are received by being Reed Solomon (RS)-encoded with a systematicRS encoding scheme and the enhanced data are received by beingRS-encoded with a non-systematic RS encoding scheme.
 5. A method ofprocessing digital broadcast data in a digital television (DTV)receiving system, the method comprising: receiving, by a tuner, abroadcast signal including a data group, the data group comprisingenhanced data, known data sequences and signaling information, whereinat least two of the known data sequences are spaced 16 segments apart,wherein an ith segment in the data group has main data and M consecutiveenhanced data bytes, an (i+1)th segment in the data group has main dataand L consecutive enhanced data bytes, and an (i+2)th segment in thedata group has main data and K consecutive enhanced data bytes, andwherein M<L<K; demodulating, by a demodulator, the broadcast signal;compensating, by an equalizer, a channel distortion of the demodulatedbroadcast signal using at least one of the known data sequences togenerate an equalized broadcast signal; inner decoding, by an innerdecoder, the equalized broadcast signal; and outer decoding, by an outerdecoder, the inner-decoded broadcast signal.
 6. The method of claim 5,wherein the data group comprises a plurality of regions, wherein eachregion comprises at least one segment, wherein enhanced data included inat least a first region of the plurality of regions are received bybeing encoded at a coding rate of 1/X, and wherein enhanced dataincluded in at least a second region of the plurality of regions arereceived by being encoded at a coding rate of 1/Y, wherein X≠Y.
 7. Themethod of claim 6, wherein a value of X is equal to 2, and a value of Yis equal to
 4. 8. The method of claim 7, wherein the main data arereceived by being Reed Solomon (RS)-encoded with a systematic RSencoding scheme and the enhanced data are received by being RS-encodedwith a non-systematic RS encoding scheme.